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Imagining the giant hippos, monstrous sharks, and sea beasts of an underwater Silicon Valley

Construction site at the Calaveras Dam in the East Bay hills.

Digging up ancient worlds

When construction workers break into the earth’s surface, it’s not unusual for them to discover ancient worlds. Last year, crews unearthed the remains of three mammoths and one giant bison in San Francisco. While working at the Caldecott Tunnel, fossil hunters discovered the remains of camels that once roamed the East Bay. There are actually provisions in California’s environmental laws that require anyone doing major digging projects to call fossil experts first, just in case. So when work began near Fremont to rebuild the Calaveras Dam, paleontologist Jim Walker was called to the scene to hunt for fossils. He expected to find a few, but the count surpassed 600.

Walker is something of a time traveler.

“I get paid to go for hikes and look for fossils,” Walker says. “It’s kind of like detective work. You can try to figure out what the world looked like way back when and what was going on.”

Right now, he’s trying to figure out what was going on way back when in a remote canyon in the Southeast Bay.

“It's up in the hills behind Milpitas, in Fremont,” Walker says. “It's actually a very pretty spot. We have a view of the Calaveras Reservoir, and from below we have the dam and all the act of construction.”

The area where Walker does his digging is pastoral and dry. Today, it’s inhabited mostly by construction workers operating dump trucks and playing with bulldozers. They’re working on making the Calaveras Dam safer in case of a future earthquake. But, Walker says he can’t help thinking about the distant past.

Walker says the fossils found here are over 20 million years old. Back then, the likes of Google and Apple wouldn’t rule Silicon Valley. There’d be no Silicon Valley. There’d just be a treacherous, unending jungle inhabited by the entire cast of Jurassic Park. You know, the whole dinosaur gang, from the loving and motherly duck-billed Maiasaura to Tyrannosaurus Rex.

Not quite any old day at the beach

Or not. Dinosaurs were long gone 20 million years ago. In reality, the world Walker is digging up was from the Miocene Epoch. Walker said it probably sounded like any old day at the beach.

“The coast would be near Mount Diablo,” he explains. If you were standing on that coast, Walker says, “you may have seen whales off in the distance, or dolphins swimming close to shore [and] a seal head pop up in the breakers.”

All in all, it would have sounded very 2014. Except, Walker says, “about 20 million years ago, we had these whales, Desmostylus, an extinct order of marine mammals. They looked kind of like a hippo, and they lived across the California coast.”

Desmostylus rendering by Dmitry Bogdanov.

He’s also found fossils of other crazy-big water animals, including one that belonged to a Megalodon. A Megalodon is a big shark that scientists think was almost 60 feet long and could crush the skull of a prehistoric whale as easily as a grape.

“It looked a lot like a great white [shark],” Walker says. “It was quite a bit larger. It's space in the environment is now taken up by things like killer whales and stuff like that.”

Fault lines keep wandering

Sea beasts lived, and sea beasts died. They sunk to the bottom of the ocean. Over time, the landscape changed and the water went away.

“Probably the big event that would have changed the way the area looked was about 15 million years ago,” Walker says. “The San Andreas fault system would have started to propagate up this way.”

The San Andreas fault formed just about 20 million years ago. The central coast, scientists think, moved north, thanks to the rumbling and shaking caused by earthquakes along this fault line. Imagine the 1906 earthquake happening several times over, sometimes on smaller scales, for millions of years, giving California’s landscape periodic makeovers over and over again.

“So, from that point on we see the development of site slip happening and things starting to look, at least geologically, a lot like they are today,” Walker says.

The world keeps moving. And, someday, someone might spend their day job looking for fossils of us. For now, though, we’re still here, trying to get our dams, our buildings, and our worlds retrofitted in an attempt to keep it that way. But, just a warning: if the Calaveras Dam failed during the time of an earthquake, experts say a 30-foot-high wall of water would rush towards Fremont and Interstate 880. It wouldn’t be the end of the world, though. The world would just look slightly different.